<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script src="https://unpkg.com/vue@next"></script>

    <div id="app">
        <todo-item></todo-item>
    </div>

    <script>
        const vueOpt = {

        }

        const app = Vue.createApp(vueOpt);

        app.component('todo-item', {
            data(){
                return {
                    count: 2
                }
            },
            methods:{
                clickEvent(){
                    this.count++;
                }
            },

            template: `
                <div v-once>
                    <button @click="clickEvent">
                        clickMe
                    </button>
                    <h1>1231321afsdasdfasfasfsfa</h1>
                    
                    <div>{{count}}</div>
                </div>
            `
        });

        app.mount('#app');
    </script>
</body>
</html>